I'm trying to find lecture notes of Mahowald and Unell, titled "Lectures on Bott periodicity in stable and unstable homotopy at the prime 2". Does anyone happen to know if a copy exists online (and if it does, where I can find it)?

It is cited in Peter May's "Applications and generalizations of the approximation theorem", and in Mahowald's "Some homotopy classes generated by $\eta_j$". Both sources cite specific sections from the document, and in the latter reference, it is said to have been submitted to Springer Lecture Notes Series. Charles Rezk pointed out to me that it's also referenced in footnote 1 of Kuhn's "Geometry of James-Hopf maps", where it's said that the document dates from 1977.